KR101483126B1 - Organic eletrolyte and lithium battery using the same - Google Patents

Abstract

The present invention relates to a lithium salt; An organic solvent containing a high-boiling solvent and a low-boiling solvent; And a silane-based compound represented by the following formula (1): < EMI ID = 1.0 >

≪ Formula 1 >

In the formula,

N is an integer of 1 to 5,

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and Z refer to the detailed description of the invention.

INDUSTRIAL APPLICABILITY The organic electrolytic solution and the lithium battery employing the organic electrolytic solution of the present invention can suppress the decomposition of the electrolyte and improve the cycle characteristics and suppress the deterioration of the service life.

Description

[0001] The present invention relates to an organic electrolytic solution and a lithium battery employing the organic electrolytic solution,

The present invention relates to an organic electrolytic solution and a lithium battery including the same. More particularly, the present invention relates to an organic electrolytic solution and a lithium battery including the same, This improved organic electrolytic solution, a lithium battery having improved cyclic characteristics by employing such organic electrolytic solution.

BACKGROUND ART [0002] With the recent development of the electronic industry, portable and wireless electronic devices such as portable telephones, digital cameras, and notebook computers are rapidly moving, and there is a growing demand for secondary batteries having lightweight, compact and high energy density as their driving power sources have. Among these batteries, a lithium-containing metal oxide showing a voltage of 4 V is used as a positive electrode active material, and a nonaqueous electrolyte lithium battery using a carbonaceous material capable of absorbing and discharging lithium as a negative electrode is a battery having high voltage and high energy density Many researches have been carried out.

The average discharge voltage of the lithium battery is about 3.6 to 3.7 V, which is higher than other alkaline batteries, nickel metal hydride batteries, and nickel-cadmium batteries. However, in order to obtain such a high driving voltage, An electrochemically stable electrolyte composition at 4.2 V is required. For this purpose, a mixture of a cyclic carbonate-based solvent such as ethylene carbonate, propylene carbonate, and butylene carbonate is mainly used as an electrolytic solution.

Among them, the ethylene carbonate electrolyte has a problem in that stability and thermal stability of the battery are lowered due to electrolyte decomposition and gas generation at a high voltage. In order to solve such problems, researches have been actively conducted to use propylene carbonate having high voltage stability. However, when a propylene carbonate electrolyte is used, solvent decomposition reaction and co-intercalation are continuously generated on the surface of the cathode electrode to form a solid electrolyte interface (SEI) And the solvent and the lithium ion are simultaneously inserted into the carbon, resulting in a problem that the charging and discharging efficiency is lowered.

The SEI coating inhibits the reaction between lithium ions and carbon anodes or other materials during charging and discharging after initial formation, and functions as an ion tunnel. The ion tunnel plays a role of suppressing the collapse of the carbon cathode structure by co-intercalating the organic solvent of the electrolytic solution having a large molecular weight, which is solvated by lithium ion, together with the carbon anode. Therefore, when the SEI film is formed, the lithium ion does not react with the carbon anode or the other material, and the amount of the lithium ion is reversibly maintained.

However, due to repeated expansion and contraction of the electrode plate and partial overvoltage as the charge and discharge progresses, the passivation layer such as the SEI film gradually collapses with time and reacts with the surface of the negative electrode exposed to the surrounding electrolyte The side reaction is continuously caused. The main gases generated at this time are CO, CO ₂ , CH ₄ , C ₂ H ₆ and the like depending on the kind of the carbonate used and the anode active material, and the pressure inside the cell rises due to continuous gas generation, There is a problem.

Further, the carbonate-based electrolyte is decomposed according to the graphite-based negative electrode active material, and the carbon material is peeled off, thereby deteriorating battery characteristics such as electric capacity, cycle characteristics, and storage characteristics. Particularly, this phenomenon occurs remarkably in an electrolytic solution containing propylene carbonate, and propylene carbonate is decomposed on the cathode at the time of initial charging, which causes a decrease in the initial capacity.

As a method for suppressing the decomposition of the cyclic carbonates by the graphite anode active material and the detachment of the carbon material, a method of suppressing decomposition of the electrolyte by adding crown ether to the electrolyte based on propylene carbonate and ethylene carbonate has been attempted. Expensive crown ethers must be added in a large amount, resulting in deteriorated economical efficiency and insufficient improvement of battery characteristics.

Japanese Patent Application Laid-Open No. 8-45545 also discloses that vinylene carbonate is added to propylene carbonate and ethylene carbonate base to inhibit decomposition of the electrolyte solution. According to this method, vinylene carbonate as an additive is reduced to a negative electrode upon charging to form an insoluble film on the surface of graphite, thereby suppressing the reduction of solvents such as propylene carbonate and ethylene carbonate.

However, such a method using vinylene carbonate fails to generate a complete SEI film at the time of initial charging, and cracks are generated in the film as the charge and discharge are repeated at room temperature, and vinylene carbonate is decomposed and consumed again at this portion Therefore, there is a problem that a stable cycle characteristic can not be obtained. In addition, although the lifetime characteristics are improved when the content of vinylene carbonate is increased, there is a problem that the low-temperature discharge capacity is rapidly lowered and high-temperature swelling occurs at high temperature.

The first problem to be solved by the present invention is to provide an organic electrolytic solution forming a uniform and dense SEI before a solvent decomposition reaction takes place using a substance in which a decomposition (reduction) reaction occurs at a potential higher than the decomposition potential of a carbonate- will be.

A second problem to be solved by the present invention is to provide a lithium battery employing the organic electrolyte solution.

According to an aspect of the present invention,

Lithium salts;

Non-aqueous organic solvents; And

Claims 1. An organic electrolytic solution comprising:

≪ Formula 1 >

In the formula,

N represents an integer of 1 to 5,

Z represents an electron-withdrawing functional group,

R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and each represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, a carboxyl group, an acyl group, a sulfonyl group, a carboxyaldehyde group, , A quaternary ammonium group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, An aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 2 to 20 carbon atoms A substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms, an aralkyloxycarbonyl group having 8 to 30 carbon atoms, or a substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms I will.

According to one embodiment of the present invention, the electron-withdrawing functional group is preferably a cyano group, a nitro group, a halogen atom, or a substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms.

According to an embodiment of the present invention, n has a value of 1.

According to one embodiment of the present invention, the content of the compound of Formula 1 is 0.01 to 10% by weight based on the total weight of the organic electrolytic solution.

According to one embodiment of the present invention, the content of the compound of Formula 1 is 1 to 5% by weight based on the total weight of the organic electrolytic solution.

According to an embodiment of the present invention, the non-aqueous organic solvent is preferably a mixed organic solvent comprising a high-boiling solvent and a low-boiling solvent.

According to one embodiment of the present invention, the non-aqueous organic solvent is one or more selected from the group consisting of cyclic carbonates, non-cyclic carbonates, aliphatic carboxylic acid esters, acyclic ethers, cyclic ethers, alkyl phosphate esters, Two or more are preferable.

According to one embodiment of the present invention, the cyclic carbonate is preferably one or more selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate.

According to one embodiment of the invention, the lithium salt is _{LiPF 6, LiBF 4, LiAsF 6} , LiClO 4, LiCF 3 SO 3, LiSbF 6, CF 3 SO 3 Li, LiN (SO 2 CF 3) 2, LiC 4 F ₃ SO _3, LiAlF ₄ , _{LiAlCl 4, LiN (SO 2 C} 2 F 5) 2, LiN (C X F 2X + 1 SO 2) (C y F 2 + y SO 2) (where, x and y are natural numbers), LiCl and LiI One or two or more selected from the group consisting of

According to one embodiment of the present invention, the compound of Formula 1 is preferably a compound of Formula 2:

(2)

In order to achieve the second object,

An organic electrolytic solution as described above;

anode;

cathode; And

And a separator interposed between the positive electrode and the negative electrode.

Hereinafter, the present invention will be described in more detail.

The organic electrolytic solution according to the present invention causes the decomposition (reduction) reaction at a potential higher than the decomposition potential of the organic solvent used in the electrolytic solution by using the compound of Formula 1 as an additive, The SEI coating is uniformly formed on the electrode surface.

The coating film formed using the compound of Formula 1 enables charging and discharging of lithium ions and plays a role of suppressing electrolyte decomposition reaction and co-intercalation of organic solvent and lithium ion on the surface of the electrode, Thereby reducing the exposure of the new electrode surface due to the volume expansion of the electrode by the electrode, thereby suppressing side reactions occurring on the electrode surface. That is, by using the compound of formula (1), an SEI coating modified on the electrode surface is uniformly formed to inhibit electrolyte decomposition to improve the cycle characteristics of the lithium battery and to suppress the deterioration of service life. The cycle characteristics of the lithium battery employing the organic electrolytic solution can be improved.

The additive used in the organic electrolytic solution of the present invention has a structure represented by the following formula (1)

≪ Formula 1 >

N represents an integer of 1 to 5,

Z represents an electron-withdrawing functional group,

R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and each represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, a carboxyl group, a sulfonyl group, a carboxyaldehyde group, A substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroalkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted carbon atom number of 2 to 30, a substituted or unsubstituted aralkyl group having 2 to 30 carbon atoms, A substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 6 to 30 carbon atoms, A substituted or unsubstituted arylalkyl group having 7 to 30 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, a substituted or unsubstituted carbon atom number 1 A substituted or unsubstituted alkoxycarbonyl group having 2 to 20 carbon atoms, a substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms, an aralkyloxycarbonyl group having 8 to 30 carbon atoms, or a substituted or unsubstituted carbonyl group Represents a haloalkyl group of 1 to 20 in embroidery.

As used herein, the term "acyl group" includes, for example, aliphatic acyl having 2 to 20 carbon atoms such as acetyl, propionyl and the like; And an aromatic acyl group having 7 to 30 carbon atoms such as benzoyl.

The term "aliphatic acyl" as used herein refers to a radical of the formula alkyl-C (O) -, alkenyl-C (O) - and alkynyl-C (O) derived from an alkane-, alkene- or alkynecarboxylic acid Point. Examples of such aliphatic acyl radicals include, but are not limited to, acetyl, propionyl, butyryl, valeryl, 4-methylvaleryl, acryloyl, crotyl, propionyl and methylpropionyl.

The alkyl group having 1 to 20 carbon atoms which is a substituent used in the present invention has a linear or branched structure and preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms. Alkyl groups are preferred. Specific examples thereof include methyl, ethyl, propyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl and hexyl. At least one hydrogen atom contained in the alkyl group may be substituted with a halogen atom, , Cyano group, and the like.

An alkoxy group having 1 to 20 carbon atoms as a substituent used in the present invention has a structure of -O-alkyl, and the oxygen atom is bonded to the main chain. The alkoxy group is preferably an alkoxy group having 1 to 12 carbon atoms, more preferably an alkoxy group having 1 to 8 carbon atoms, and most preferably an alkoxy group having 1 to 4 carbon atoms. Examples of such an alkoxy group include a methoxy group, an ethoxy group, and a propoxy group, and at least one hydrogen atom contained in the alkoxy group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

The alkenyl group having 2 to 20 carbon atoms, which is a substituent used in the present invention, has a straight-chain or branched structure and means that at least one unsaturated double bond is contained in the alkyl group defined above. The at least one hydrogen atom contained in the alkenyl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

The alkynyl group having 2 to 20 carbon atoms, which is a substituent used in the present invention, has a straight-chain or branched structure and means that at least one unsaturated triple bond is contained in the alkyl group defined above. The at least one hydrogen atom contained in the alkynyl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

The aryl group having 6 to 30 carbon atoms as the substituent used in the present invention means a carbocyclic aromatic system containing at least one aromatic ring, preferably an aryl group having 6 to 20 carbon atoms, and more preferably an aryl group having 6 to 10 carbon atoms. The aromatic rings may be attached together or fused together by a pendant method. At least one hydrogen atom of the aryl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like. Specific examples of such an aryl group include a phenyl group, a halophenyl group (e.g., o-, m- and p-fluorophenyl group, dichlorophenyl group), a cyanophenyl group, a dicyanophenyl group, a trifluoromethoxyphenyl group, halo-biphenyl group, a cyanobiphenyl group, a C ₁ -C ₁₀ biphenyl group, C ₁ -C ₁₀ alkoxy biphenyl, o-, m-, and p- group-Sat, o-, m- and p- cumenyl group, a mesityl group (N, N'-diphenyl) aminophenyl group, a pentalenyl group, an indenyl group, a naphthyl group, a halonaphthyl group, group (e. g., fluoro-naphthyl group), C ₁ -C ₁₀ alkyl naphthyl group (e.g., a methyl naphthyl group), C ₁ -C ₁₀ alkoxy-naphthyl group (e.g., methoxy naphthyl), a cyano A phenanthryl group, a phenanthryl group, a phenanthryl group, a triphenylene group, a phenanthryl group, a phenanthryl group, a phenanthryl group, a phenanthryl group, a phenanthryl group, A perylene group, a perfluorenyl group, a perfluorenyl group, a perfluorenyl group, a perphenyl group, a pentacenyl group, a tetraphenylenyl group, a hexaphenyl group, a hexacenyl group, a rubicenyl group, a norbornenyl group, A trinaphthyl group, a triphenyl group, a heptadecenyl group, a pyranthrenyl group, an obarenyl group and the like.

The alkylaryl group having 7 to 30 carbon atoms which is the substituent used in the present invention means that at least one of the hydrogen atoms of the above-defined aryl group is substituted with an alkyl group. For example, a benzyl group, but are not limited thereto. At least one hydrogen atom of the alkylaryl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

The arylalkyl group having 7 to 30 carbon atoms which is the substituent used in the present invention means that at least one of the hydrogen atoms of the alkyl group defined above is substituted with an aryl group. For example, 4-tert-butylphenyl group, 4-ethylphenyl group and the like, but are not limited thereto. At least one hydrogen atom of the arylalkyl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

The heteroalkyl group having 1 to 20 carbon atoms as the substituent used in the present invention means that the main chain of the alkyl group defined above contains a hetero atom such as an oxygen atom, a nitrogen atom, a sulfur atom or a phosphorus atom. At least one hydrogen atom of the heteroalkyl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

The heteroaryl group having 4 to 30 carbon atoms which is a substituent used in the present invention is a heteroaryl group having at least one hetero atom selected from a hetero atom, for example, an oxygen atom, a nitrogen atom, a sulfur atom and a phosphorus atom, Means that the one or more aromatic rings may be fused to each other, or may be connected to each other through a single bond or the like. At least one hydrogen atom of the heteroaryl group may be substituted with a halogen atom, a hydroxy group, a nitro group, a cyano group, or the like.

As used herein, an aryloxy group having 6 to 30 carbon atoms, which is a substituent, has the form of aryl-O-, and the aryl is as defined above.

The term "haloalkyl ", as used herein, refers to an alkyl radical to which one or more halogen substituents are attached, examples of which include chloromethyl, fluoroethyl, trifluoromethyl and pentafluoroethyl.

The compound of formula (1) can be basically divided into three parts of an electron-withdrawing functional group, a polymerizable functional group and a lithium ion conductive functional group. The compound of formula (1) is easily received from a vinyl group by an electron- Lt; / RTI > is first grafted to the electrode, e. G. Graphite surface, at a potential higher than the co-intercalation potential of the solvent. Polymerization is then carried out with the grafting, which results in the formation of an SEI film on the electrode surface. The SEI coating thus formed inhibits co-intercalation caused by continuous insertion and decomposition of the organic solvent into the interlayer structure of the electrode, and at the same time, the organic solvent-affinity functional group in the coating, that is, the lithium ion conductive functional group, The initial efficiency can be expected to be improved.

The electron withdrawing group of the compound of Chemical Formula 1 means a functional group capable of attracting electrons and the term "electron attracting property" means that when hydrogen is present at the same position on one molecule, Represents the ability to attract electrons.

Examples of such an electron attractive functional group include a halogen atom, a nitro group, a carboxyl group, a cyano group, a haloalkyl group, a carboxyl group, an alkenyl group, an alkynyl group, a carboxyaldehyde group, a carboxyamido group, an aryl group and a quaternary ammonium group. A cyano group, a nitro group, a halogen atom, or a substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms.

The compound of formula (1) is present as an additive in the organic electrolytic solution, and its content is 0.01 to 10% by weight, preferably 1 to 5% by weight based on the total weight of the organic electrolytic solution. If the content of the additive is less than 0.01% by weight, it is difficult to form an improved SEI film, and deterioration or swelling may occur during the course of the cycle. If the content is more than 10% by weight, .

Preferable examples of the compound of the formula (1) include the following compounds:

(2)

The organic electrolytic solution of the present invention basically includes a lithium salt and a non-aqueous organic solvent. The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, a mixed organic solvent composed of a high-boiling solvent and a low boiling solvent can be used. The mixing ratio of the high-boiling solvent to the low-boiling solvent is preferably 1: 1 to 1: 9, and when the ratio is out of the range, the discharge capacity and the charge / discharge life are not preferable.

Specific examples of the non-aqueous organic solvent include one or more selected from the group consisting of cyclic carbonates, non-cyclic carbonates, aliphatic carboxylic acid esters, acyclic ethers, cyclic ethers, alkyl phosphate esters and fluorides thereof have. Preferably, the nonaqueous solvent may use at least one selected from the group consisting of the cyclic carbonate, the noncyclic carbonate and the aliphatic carboxylic acid ester.

The cyclic ether, the alkylphosphoric ester, the cyclic carbonate and the noncyclic ether correspond to the high-k time solvent, and the cyclic carbonate and the aliphatic carboxylic acid ester correspond to the low boiling point solvent.

Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the noncyclic carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Propyl carbonate, methyl ethyl carbonate, and the like can be used. As the aliphatic carboxylic acid ester, methyl formate, methyl acetate, methyl propionate, ethyl propionate and the like can be used.

Examples of the non-cyclic ethers include gamma-lactones, 1,2-dimethoxyethane, 1,2-diethoxyethane and ethoxymethoxyethane. Examples of the cyclic ether include tetrahydrofuran, 2-methyl Tetrahydrofuran and the like can be used. As the alkylphosphoric ester, dimethyl sulfoxide, 1,2-dioxolane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate and the like can be used.

The lithium salt used in the organic electrolytic solution acts as a source of lithium ions in the battery, thereby enabling operation of a basic lithium battery. Examples of such lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO _3, LiSbF _6, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) ₂ , LiC ₄ F ₃ SO _3, LiAlF ₄ , _{LiAlCl 4, LiN (SO 2 C} 2 F 5) 2, LiN (C X F 2X + 1 SO 2) (C y F 2 + y SO 2) (where, x and y are natural numbers), LiCl and LiI Or a combination thereof, but is not limited thereto.

The concentration of the lithium salt in the organic electrolytic solution is preferably about 0.5 to 2 M, the concentration of the lithium salt is less than 0.5 M, the conductivity of the electrolytic solution is lowered to deteriorate the performance of the electrolyte, and when the concentration exceeds 2.0 M, The mobility of the mobile terminal is reduced.

A lithium battery including the organic electrolytic solution of the present invention comprises a positive electrode, a negative electrode and a separator.

The positive electrode may be prepared by directly coating a positive electrode active material composition obtained by mixing a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions, a conductive agent, a binder and an organic solvent onto a current collector, casting the current collector on a separate support, And then the laminated positive electrode active material film is laminated on a current collector.

The positive electrode active material used for the positive electrode active material composition is not particularly limited, but a lithium-containing metal oxide may be used. Examples of the lithium-containing metal oxide include Li-Co composite oxide such as LiCoO ₂ , Li-Ni composite oxide such as LiNiO ₂ , Li-Mn composite oxide such as LiMn ₂ O ₄ and LiMnO ₂ , Li ₂ Cr ₂ O ₇ Li-Cr composite oxide such as Li ₂ CrO ₄ , Li-Fe composite oxide such as LiFeO ₂ , Li-V composite oxide, LiNi _x-1 Mn _x O _2x (x = _1-xy Co _x Mn _y O ₂ (0? _X ? 0.5, 0? _Y ? 0.5), and the like.

In addition to the cathode active material, carbon black is used as a conductive agent constituting the cathode active material composition, and examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate Polytetrafluoroethylene and mixtures thereof, and styrene-butadiene rubber-based polymers.

In this case, the content ratio of the cathode active material, the conductive agent, and the binder may be a level commonly used in a lithium battery, and is not particularly limited.

The current collector in which the cathode active material composition as described above is formed is not limited as long as it is used as a current collector for a positive electrode in a lithium battery, but an aluminum current collector is preferably used. The size and thickness of the current collector can be used within a range normally used in a lithium battery.

The positive electrode according to the present invention can be manufactured as follows.

First, a slurry containing a binder, a conductive agent, a cathode active material and an organic solvent is uniformly coated on one surface of a current collector, followed by drying to evaporate the organic solvent, thereby forming a cathode active material composition layer on the current collector do.

The kinds of the conductive agent and the binder constituting the slurry together with the cathode active material, the binder and the conductive agent are as described above. As the organic solvent, for example, dimethyl carbonate, ethyl methyl carbonate, Cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, gamma-butyrolactone, N-methylpiperazine, N-methylpyrrolidone, and the like; cyclic carbonates such as diethyl carbonate, dipropyl carbonate, dimethoxyethane, diethoxyethane, fatty acid ester derivatives, Rawlidone, acetone, water or mixtures thereof may be used.

The negative electrode may be prepared by preparing a negative electrode active material slurry by mixing a negative electrode active material, a conductive agent, a binder and an organic solvent in the same manner as in the preparation of the positive electrode described above. The negative electrode active material slurry is directly coated on the copper current collector, cast on a separate support, The peeled negative electrode active material film is laminated on the copper current collector to obtain a negative electrode. In this case, the content of the negative electrode active material, the conductive agent, the binder and the organic solvent can be used within the range of ordinary use in a lithium battery, and there is no particular limitation.

As the negative electrode active material, a lithium metal, a lithium alloy, a carbon material, or graphite is used. As the conductive agent, the binder and the organic solvent in the negative electrode active material composition, the same materials as those of the positive electrode may be used. In some cases, a plasticizer may be further added to the cathode active material composition and the cathode active material composition to form pores inside the electrode plate.

The positive electrode and the negative electrode can be separated by a separator, and the separator can be used without limitation as long as it is commonly used in a lithium battery. Particularly, it is preferable that the electrolytic solution has a low resistance against the ion movement of the electrolyte and an excellent ability to impregnate the electrolyte. For example, a material selected from the group consisting of glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and the above combination may be in the form of nonwoven fabric or woven fabric. More specifically, in the case of a lithium ion battery, a rewindable separator made of a material such as polyethylene or polypropylene is used. In the case of a lithium ion polymer battery, a separator having an excellent ability to impregnate an organic electrolyte is used. It can be manufactured according to the method.

That is, a separator composition is prepared by mixing a polymer resin, a filler and a solvent, and then the separator composition is directly coated on the electrode and dried to form a separator film, or after casting and drying the separator composition on a support, And the separator film is laminated on the electrode.

The polymer resin is not particularly limited, and all the materials used for the binder of the electrode plate can be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and mixtures thereof. Particularly, it is preferable to use a vinylidene fluoride / hexafluoropropylene copolymer having a hexafluoropropylene content of 8 to 25 parts by weight.

A separator is disposed between the positive electrode plate and the negative electrode plate as described above to form a battery structure. This battery structure is wound or folded into a cylindrical battery case or a rectangular battery case, and then an organic electrolyte solution of the present invention is injected to complete a lithium battery.

Further, the cell structure may be laminated by a bi-cell structure having a structure of a positive electrode / separator / negative electrode / separator / positive electrode or a structure of a laminated cell in which the structure of a unit cell is repeated, then impregnating the organic electrolyte with the organic electrolyte solution of the present invention, Is sealed in a pouch, a lithium polymer battery is completed.

A representative example of the lithium battery of the present invention having such a configuration is shown in Fig. 1, a lithium battery includes an electrode assembly 12 composed of a positive electrode 13, a negative electrode 15, and a separator 14 positioned between the positive electrode 13 and the negative electrode 15, (10), and sealing the upper end of the can (10) with the cap assembly (20). The cap assembly 20 includes a cap plate 40, an insulating plate 50, a terminal plate 60, and an electrode terminal 30. The cap assembly 20 is coupled with the insulating case 70 to seal the can 10.

The electrode terminal 30 is inserted into the terminal through-hole 41 formed at the center of the cap plate 40. When the electrode terminal 30 is inserted into the terminal through hole 41, a tubular gasket 46 is coupled to the outer surface of the electrode terminal 30 for insulation between the electrode terminal 30 and the cap plate 40, do. After the cap assembly 20 is assembled to the upper end of the cap 10, the electrolyte is injected through the electrolyte injection hole 42 and the electrolyte injection hole 42 is sealed by the cap 43. The electrode terminal 30 is connected to the negative electrode tab 17 of the negative electrode 15 or the positive electrode tab 16 of the positive electrode 13 to function as a negative electrode terminal or a negative electrode terminal.

The lithium battery to which the organic electrolytic solution of the present invention is applied forms a uniform and stable SEI film at the time of initial charging, thereby improving cycle characteristics and lifetime characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1: Preparation of electrolytic solution

An organic electrolytic solution was prepared by adding 5 wt% of a compound represented by the following formula (1) as an additive to an organic solvent composed of propylene carbonate and using 1M LiClO ₄ as a lithium salt.

Example 2: Preparation of electrolytic solution

3% by weight of a compound represented by the following formula (1) as an additive was added to an organic solvent (volume ratio 2: 6: 2) composed of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate, As the lithium salt, 1M LiPF ₆ was used to prepare an organic electrolytic solution.

Comparative Example 1: Preparation of electrolytic solution

An organic electrolytic solution was prepared by using 1 M LiClO ₄ as a lithium salt in an organic solvent composed of propylene carbonate.

Comparative Example 2: Preparation of electrolytic solution

Organic electrolytic solution was prepared by using 1 M LiPF ₆ as a lithium salt in an organic solvent (volume ratio 2: 6: 2) composed of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate Respectively.

Example 3: Preparation of lithium ion battery

A ratio of graphite powder MCMB (mesocarbon microbeads; manufactured by Osaka gas Chemicals Company) and N-methylpyrrolidone (NMP) to binder in which 5% by weight of polyvinylidene fluoride (PVdF) was dissolved in an amount of 95: And mixed well to prepare a slurry.

The slurry was cast on a copper foil having a thickness of 19 mu m with a doctor blade having an interval of 100 mu m to obtain an anode electrode. The anode electrode was then placed in an oven at 90 DEG C for a period of about 2 hours for primary drying to evaporate NMP, Followed by secondary drying for 2 hours to allow most of the NMP to dry. Thereafter, the electrode was rolled to obtain an anode having an electrode thickness of 60 mu m.

A coin cell of the 2016 standard was prepared by using the anode, a lithium metal as a counter electrode, a polyethylene separator, and the organic electrolytic solution obtained in Example 1, respectively.

Example 4: Preparation of lithium ion battery

The graphite powder MCMB (manufactured by Osaka Gas Chemicals Company) and silicon (Si) powder were ball-milled to form a composite, and then polyvinylidene fluoride (PVdF) was added to N-methylpyrrolidone (NMP) Weight% The ratio of the dissolved binder to the conductive material was added to the agate mortar at a weight ratio of 70:15:15 and mixed well to prepare a slurry.

The slurry was cast on a copper foil having a thickness of 19 mu m with a doctor blade having an interval of 100 mu m to obtain an anode electrode. The anode electrode was then placed in an oven at 90 DEG C for a period of about 2 hours for primary drying to evaporate NMP, Followed by secondary drying for 2 hours to allow most of the NMP to dry. Thereafter, the electrode was rolled to obtain an anode having an electrode thickness of 60 mu m.

A coin cell of the 2016 standard was prepared by using the anode, using a lithium metal as a counter electrode, using a polyethylene separator, and using the organic electrolytic solution obtained in Example 2, respectively.

Comparative Example 3: Manufacture of lithium ion battery

A coin cell was prepared in the same manner as in Example 3 except that the organic electrolytic solution prepared in Comparative Example 1 was used.

Comparative Example 4: Manufacture of lithium ion battery

A coin cell was prepared in the same manner as in Example 4 except that the organic electrolytic solution prepared in Comparative Example 2 was used.

Experimental Example 1: Test of charge / discharge characteristics of a battery

The coin cell having the cell capacity of 1.38 mAh produced in Example 3 and Comparative Example 3 was subjected to constant current charging until reaching 0.001 V with respect to the Li electrode at a current of 0.1 C rate, While the current was charged at a constant voltage of 0.02C per cell capacity. Then, a constant current discharge was performed at a current of 0.1 C rate of the cell capacity until the voltage reached 1.5 V to obtain the charge / discharge capacity.

Experimental Example 2: Test of charge / discharge characteristics of a battery

The coin cell having the cell capacity of 2.36 mAh produced in Example 4 and Comparative Example 4 was charged at a constant current until the voltage reached 0.001 V with respect to the Li electrode at a current of 0.1 C rate, V, the charge / discharge capacity was obtained by performing a constant current discharge with a current of 0.1 C rate of the cell capacity. The charge / discharge efficiency was calculated from this. The charge-discharge efficiency is expressed by the following equation (1).

&Quot; (1) "

Initial charging / discharging efficiency (%) = discharging capacity of 1st cycle / charging capacity of 1st cycle

2 shows that in Comparative Example 3 using a single solvent, intercalation of lithium ions does not occur, but in Example 3 in which the present additive is introduced, SEI is formed on the surface of the electrode, resulting in smooth insertion and removal of lithium ions And the efficiency was as high as 80%.

In FIG. 3, in Example 4, although the cycle life lasts for a small amount in the initial stage, the cycle characteristics are improved as compared with Comparative Example 4.

1 is a schematic view showing the structure of a lithium battery of the present invention.

2 is a graph showing the charging / discharging efficiency of the first cycle of the battery obtained according to Example 3 and Comparative Example 3. Fig.

3 is a graph showing the cycle life of the battery obtained in Example 4 and Comparative Example 4. Fig.

Claims (10)

Lithium salts; Non-aqueous organic solvents; And 1. An organic electrolytic solution comprising: ≪ Formula 1 >

In the formula, N represents an integer of 1 to 5, Z represents an electron-withdrawing functional group, Wherein the electron-withdrawing functional group is a cyano group, a nitro group, a halogen atom, or a substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and each represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, a carboxyl group, an acyl group, a sulfonyl group, a carboxyaldehyde group, , A quaternary ammonium group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, An aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 2 to 20 carbon atoms A substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms, an aralkyloxycarbonyl group having 8 to 30 carbon atoms, or a substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms I will. delete The method according to claim 1, Wherein n has a value of 1. The method according to claim 1, Wherein the content of the compound of Formula 1 is 0.01 to 10% by weight based on the total weight of the organic electrolytic solution. The method according to claim 1, Wherein the content of the compound of Formula 1 is 1 to 5% by weight based on the total weight of the organic electrolytic solution. The method according to claim 1, Wherein the non-aqueous organic solvent is a mixed organic solvent consisting of a high-dielectric solvent and a low-boiling solvent. The method according to claim 1, Wherein the non-aqueous organic solvent is at least one selected from the group consisting of cyclic carbonates, non-cyclic carbonates, aliphatic carboxylic acid esters, acyclic ethers, cyclic ethers, alkyl phosphate esters and fluorides thereof. . 8. The method of claim 7, Wherein the cyclic carbonate is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. The method according to claim 1, Wherein the compound of formula (1) is a compound of formula (2). (2)

10. An organic electrolytic solution according to any one of claims 1 to 9, anode; cathode; And And a separator interposed between the positive electrode and the negative electrode.

Images